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Letters to the Editor
cently published by Taylor et al (2), who reported an overall
Recent eLetters to the Editor are available at radiology.rsnajnls
success rate of 93% with an average dose of 300 units of
.org. eLetters that are no longer posted under ‘‘Recent eLet-
thrombin. In addition, use of a lower dose of thrombin may
ters’’ can be found as a link in the related article or by brows-
potentially reduce the likelihood of complications. At this
ing through past Tables of Contents.
time, the minimal necessary thrombin dose to achieve pseu-doaneurysm thrombosis is the subject of ongoing clinicalresearch. Using the same logic that was just hypothesized, we
Iatrogenic Femoral Pseudoaneurysms
elected to inject the cavity adjoining the native vessel in allfour cases. Immediate thrombosis of all lobes was observed
with the injection of an average of 200 units (1 mL) ofthrombin.
No complications occurred, and no recurrence of pseudo-
Department of Radiology, Hadassah University HospitalPO Box 12141, Jerusalem 91120, Israel
aneurysm was demonstrated after an average follow-up of 9
months (range, 5–12 months). It is possible that small samplenumbers introduced bias into our results. The difference in
the pseudoaneurysm volume in the two reports may explain
We would like to comment on the recently published article
why a smaller dose of thrombin was effective in our series
by Drs Sheiman and Brophy (1). The authors describe a 100%
(200 units [1 mL] vs minimum of 1,500 units). It is not clear
success rate of percutaneous thrombin injection for the treat-
from the report by Drs Sheiman and Brophy what dilution of
ment of simple pseudoaneurysms, whereas their success rate
thrombin was used, and, consequently, what volume was
for complex pseudoaneurysms was only 56% (five of nine
pseudoaneurysms). Complex pseudoaneurysm architecture
Thus far, we have not encountered any technical difficulty
was associated with a procedure failure. Because of realistic
in inserting the needle into the cavity nearest the native
concern about possible native vessel thrombosis or emboli-
vessel by using continuous ultrasonographic guidance. The
zation if the lobe directly connected to the native vessel was
needle tip and the injection are directed away from the neck
to be injected, Drs Sheiman and Brophy elected to inject the
of the pseudoaneurysm, and injection is continued until
farthest removed lobe first and then perform a second injec-
thrombosis occurs. The volume range of the simple pseudo-
tion in the directly connected lobe if persistent or recurrent
aneurysms in the remaining 10 patients in our series varied
flow was observed. It is noted that “. . . we cannot exclude
from 5 to 20 cm3 (median, 8.5 cm3). This volume range is also
the possibility that direct injection into this lobe (directly
smaller than that in the Sheiman and Brophy report (6.4 –
joined to the native vessel) could cause thrombosis, eliminate
53.0 cm3; mean, 15.8 cm3 Ϯ 10.4). However, our maximal
flow in the more distal lobe, and lead to total spontaneous
thrombin dosage was 600 units (mean, 250 units) as opposed
thrombosis of the entire pseudoaneurysm.”
to 1,000 units (1). We had nine of 10 procedural successes, for
Comparison of this report with our recent experience with
an overall success rate of 93% (13 of 14 successes). The single
14 patients who had iatrogenic femoral pseudoaneurysms
failure occurred in a patient who received warfarin sodium
may be useful in helping to determine the most appropriate
(Coumadin) therapy and in whom a second thrombin injec-
technique for this emerging new therapy. We performed
tion after 48 hours also failed. The patient underwent surgical
percutaneous topical thrombin (Thrombin-JMI; Jones Medi-
repair. A simple pseudoaneurysm with a single neck was
cal Industries, St Louis, Mo) injection after obtaining local
institutional review board approval. All patients failed a trial
It may be that the trade-off between theoretical safety of
of nonguided external compression that was continued for a
the technique proposed by Drs Sheiman and Brophy is obvi-
minimum of 2 and a maximum of 9 days. Heparin therapy
ated by the theoretical additional risk of a second thrombin
was discontinued prior to thrombin injection but was recom-
injection. We propose that injection of the lobe nearest to
menced immediately afterward in four cases. Four of the 14
the native vessel is no more risky than injection into any
patients had a complex pseudoaneurysm, three of whom had
simple pseudoaneurysm. Undoubtedly, as the frequency of
two interconnecting lobes, one had four interconnecting
this new therapy increases, the incidence of complications
lobes, and all had a single neck. None of these patients were
will also increase. However, controlled image-guided injec-
receiving anticoagulant therapy, but two were receiving an-
tion into the nearest lobe of a complex pseudoaneurysm,
tiplatelet drugs. The median pseudoaneurysm volume of 7.5
with the lowest possible thrombin dose, appears to be a
cm3 (range, 5–12 cm3) in the four complex pseudoaneurysms
was lower than that in the cases just described (mean Ϯ SD,23.3 cm3 Ϯ 12.8). The maximal complex pseudoaneurysmdiameter in our series was 5 cm (range, 2.5–5.0 cm).References
Despite many similarities between our technique and that
Sheiman RG, Brophy DP. Treatment of iatrogenic femoral
of Drs Sheiman and Brophy (1), there are some important
pseudoaneurysms with percutaneous thrombin injection: expe-rience in 54 patients. Radiology 2001; 219:123–127.
differences. First, from the outset of our experience, we chose
Taylor BS, Rhee RY, Muluk S, et al. Thrombin injection versus
to use a low concentration of bovine thrombin (ie, 200
compression of femoral artery pseudoaneurysms. J Vasc Surg
units/mL saline). This decision was based on the results re-
292 ⅐ Radiology ⅐ January 2002Drs Sheiman and Brophy respond:References1.
Kent KC, McArdle CR, Kennedy B, Baim DS, Anninos E, Skillman
We are in agreement with Dr Bloom that the technique for
JJ. A prospective study of the clinical outcome of femoral
the treatment of iatrogenic femoral pseudoaneurysms with
pseudoaneurysms and arteriovenous fistulas induced by arterial
thrombin has not yet been optimized and thank him for
puncture. J Vasc Surg 1993; 17:125–133.
contributing his experience. However, on the basis of the
Kang SS, Labropoulos N, Mansour A, Baker WH. Percutaneousultrasound guided thrombin injection: a new method for treating
data presented, we cannot agree with the recommendation
postcatheterization femoral pseudoaneurysms. J Vasc Surg 1998;
that performing image-guided injection into the cavity of a
complex pseudoaneurysm directly joined to the native vesselis reasonable. First, the median volume of Dr Bloom’s four
Robert G. Sheiman, MD, and David P. Brophy, MD
complex pseudoaneurysms (7.5 cm3) was approximately one-
Department of Radiology, Beth Israel Deaconess
third that of ours (20.0 cm3). Hence, the volumetric flow
encountered in our complex pseudoaneurysms was nearly
three times as great. The lack of complications from the
e-mail: rsheiman@caregroup.harvard.edu
injection of thrombin into the lobe directly in contact withthe native vessel in his four cases does not necessarily extrap-olate into a low acceptable complication rate for our cases orfor this technique in general.Schmorl Nodes: Lack of Relationship between
Additionally, Dr Bloom does not formally present his def-
Degenerative Changes and Osteopenia
inition of a complex pseudoaneurysm. A clear distinctionbetween a pseudoaneurysm that we formally define as com-
plex (multiple compartments separated by a patent tract,
Emilio Gonza´lez-Reimers,* Marı´a Mas-Pascual,* Matilde
which has a diameter smaller than the minimal dimension of
Arnay-de-la-Rosa,† J. Velasco-Va´zquez,† and F. Santolaria-
the smallest lobe) and one, for example, that has a single lobe
but is potentially considered complex due to multiple septa-
Department of Internal Medicine, Hospital Universitario
tions must be made. Although Dr Bloom’s proposal may turn
out to be correct, he cannot advocate this approach on the
basis of experience with four small complex pseudoaneu-
Department of Prehistory, Anthropology, and
rysms (at least two of which, per data published at our insti-
tution [1], could potentially thrombose spontaneously). Pres-
Universidad de La Laguna, Tenerife, Canary Islands, Spain†
ently, the theoretical safety offered by our technique hasbeen successfully applied to 11 additional complex pseudoan-
eurysms (all with total volumes exceeding 6 cm3) without
We have read with interest the article by Drs Pfirrmann and
complication. Therefore, the theoretical additional risk of a
Resnick (1) in which the relationship between Schmorl nodes
second injection does not appear to be an issue.
and degenerative spinal changes was analyzed. Herniation of
Dr Bloom also required lower thrombin doses for the suc-
the nucleus pulposus of the intervertebral disk into the adja-
cessful treatment of his four complex and 10 simple pseudo-
cent vertebral body leads to the formation of Schmorl nodes.
aneurysms, when compared with those in our cases. He right-
Several mechanisms may underlie the formation of Schmorl
fully identifies that this difference may be the result of his
nodes (2,3), including degeneration of the cartilage and al-
smaller pseudoaneurysm volumes. Indeed, Kang et al (2)
terations of the subchondral bone of the vertebral body,
found a direct relationship between pseudoaneurysm size
which in turn may be due to developmental defects or sys-
and the dose required for obliteration. This has also been our
experience, though other factors such as patient coagulation
In the Pfirrmann and Resnick study, Schmorl nodes were
status and blood pressure likely play a role. However, there is
associated with moderate but not advanced degenerative
implication in his letter that the larger doses of thrombin
changes. We have conducted a similar study to test whether
used in our study may not be warranted. We point out that
Schmorl nodes are related to degenerative changes of the spine
the proposal by Dr Bloom to use the lowest possible throm-
or to vertebral osteopenia in vertebrae belonging to pre-His-
bin dose for successful pseudoaneurysm treatment is a given
panic inhabitants buried in a collective cave on the island of El
and one that we have adhered and continue to adhere to.
Hierro, in the Canary Archipelago. The sample was composed of
Use of lower thrombin doses for pseudoaneurysm treat-
90 T12, 151 L1, and 91 L2 vertebrae. The number and location
ment in general and treatment of a complex pseudoaneu-
of Schmorl nodes were assessed at inspection. The area of these
rysm by means of injection into the lobe that is in direct
nodules was measured. The severity of degenerative changes
communication with the native vessel may be shown to be
was recorded at both the vertebral body and the interapophy-
optimal with future research. However, we do not believe
seal articular surfaces and was graded as minimal or absent,
that either technique can currently be conclusive on the basis
slight, moderate, or severe on the basis of size and extent of
of Dr Bloom’s experience with the small number and size of
the pseudoaneurysms he presents. A technique that advo-
In 74 cases, osteopenia was assessed with histomorphometry
cates needle placement far away from the pseudoaneurysm
in undecalcified vertebral bone specimens by measuring trabec-
neck while maintaining success should still be favored at this
ular bone mass (TBM); and in 115 cases, by measuring bone
mineral density (BMD) with dual-energy x-ray absorptiometry
Volume 222 ⅐ Number 1Radiology ⅐ 293
(QDR 2000 software w 5.54; Hologic, Boston, Mass). Conven-
Dr Gonza´lez-Reimers and colleagues analyzed the presence
tional radiographs were also obtained in all the vertebrae.
of Schmorl nodes and the degenerative changes of the spine.
We found Schmorl nodes in 16.67% of T12 vertebrae, in
Because they used whole paleontologic vertebrae, they were
47.68% of L1, and in 40.66% of L2; the total incidence was
also able to analyze the posterior elements of the spine,
37.35% (124 cases). In 61 cases, the nodes were multiple. In 107
which was not done in our work. The presented results are in
cases, the nodes were in the superior vertebral plate, whereas in
line with the results of our investigation. In the statistical
58 cases, they were in the inferior plate. In 41 cases, the nodes
analysis, Dr Gonza´lez-Reimers and co-workers found a trend
appeared in both the superior and inferior plates. There was no
for the association of Schmorl nodes with degenerative
association between degenerative changes in the vertebral body
changes of the spine. In a larger sample and with the analysis
and the Schmorl nodes (although there was a trend, ␹2 ϭ 2.68;
of the intervertebral disk height, this trend would probably
P ϭ .105), between Schmorl nodes and degenerative changes at
the interapophyseal articular surfaces, or between the area of
Osteoporosis has been emphasized as a cause of Schmorl
the Schmorl nodes and degenerative changes at both the ver-
nodes, but this correlation is not yet certain (2,3). Analysis of
tebral body and the articular surfaces. Vertebrae with Schmorl
this association is inherently difficult. Most investigations
nodes showed a significantly higher mean BMD (0.53 g/cm2 Ϯ0.11) than vertebrae without Schmorl nodes (0.44 Ϯ 0.11, t ϭ
have been performed after the formation of Schmorl nodes,
4.0, P Ͻ .001). There was also a trend for higher TBM in the
that is, after the healing of the osseous structures. With the
vertebrae with Schmorl nodes (18.25% Ϯ 5.19) than in those
healing of bone, sclerosis and callus formation increase the
without Schmorl nodes (16.11% Ϯ 5.01, t ϭ 1.72, P ϭ .089). A
BMD, and preexisting osteoporosis may be masked. Weak-
significant correlation was observed between BMD and TBM
ness of the end plate and of the underlying trabecular bone
(r ϭ 0.56, P Ͻ .001).
that is caused by reduced bone mineral density at the time of
Thus, we failed to find any relationship between vertebral
the formation of the Schmorl node seems intuitive but re-
degenerative changes and Schmorl nodes or between osteope-
nia and Schmorl nodes. The higher BMD and the nonsignifi-cantly higher TBM values of the vertebrae with Schmorl nodesare probably explained by the distorting effect of the sclerotic
References
rim that surrounds long-standing chronic Schmorl nodes.
Pfirrmann CW, Resnick D. Schmorl nodes of the thoracic andlumbar spine: radiographic-pathologic study of prevalence, char-
References
acterization, and correlation with degenerative changes of 1,650spinal levels in 100 cadavers. Radiology 2001; 219:368 –374.
Pfirrmann CWA, Resnick D. Schmorl nodes of the thoracic and
Boukhris R, Becker KL. Schmorl’s nodes and osteoporosis. Clin
lumbar spine: radiographic-pathologic study of prevalence, char-acterization, and correlation with degenerative changes of 1650
spinal levels in 100 cadavers. Radiology 2001; 219:368 –374.
Hansson T, Roos B. The amount of bone mineral and Schmorl’s
Fahey V, Opeskin K, Silberstein M, Anderson R, Briggs C. The
nodes in lumbar vertebrae. Spine 1983; 8:266 –271.
pathogenesis of Schmorl’s nodes in relation to acute trauma: anautopsy study. Spine 1998; 23:2272–2275.
Resnick D, Niwayama G. Intravertebral disk herniations: cartilag-
Christian W. A. Pfirrmann, MD,* and Donald Resnick, MD†
inous (Schmorl’s) nodes. Radiology 1978; 126:57– 65.
Department of Radiology, Orthopedic University
Drs Pfirrmann and Resnick respond:
Forchstrasse 340, Zurich CH-8008, Switzerland*
We appreciate the comments by Dr Gonza´lez-Reimers and
colleagues and the interest in our study (1). In their letter,
Department of Radiology, Veterans Affairs San Diego
they mention two interesting points that deserve comment.294 ⅐ Radiology ⅐ January 2002